Aboriginal patch burning practices are unlikely to have stopped climate-driven megafires sweeping across the Australian arid zone in pre-European times, a new study has found.
Drawing on multiple lines of evidence, from Aboriginal myth to satellite imagery, a team led by University of New England (UNE) fire ecologist Dr Boyd Wright uncovered strong evidence that megafires were part of the arid Australian environment under pre-European Aboriginal management.
The study found that the main factor driving megafires was — and still is — climate, specifically very wet periods followed by a dry time.
The findings have implications for management of forests in eastern Australia, where patch burning is being championed as a response to the 2019-20 megafires.
"The message is not that patch burning has no value," Dr Wright said. "Patch-burning is a great way to promote edible food and medicinal plants for Aboriginal people. Early post-burn food resources are also important for wildlife, and targeted patch-burning may assist in protecting areas of fire-sensitive vegetation."
"But the idea that patch burning will prevent megafires does not hold up, at least in the spinifex grasslands that we studied. What drives megafires in these systems is a very wet period, which produces a lot of vegetation growth, followed by a dry period, when that vegetation becomes standing fuel for fires."
Dr Wright wanted to investigate pre-European fire regimes since undertaking his PhD in Central Australia in the early 2000s.
"I was doing fire mapping in Alice Springs, and seeing that during big burns, fire was going over or around areas that had recently been patch burned. And yet we were repeatedly being told that patch burning was the way to suppress big fires."
Image: Fire in Central Australia's spinifex rangelands.
The study led by Dr Wright, just published in the journal Frontiers of Ecology and Evolution, cast a wide net.
Researchers examined the records left by the first European explorers of the arid zone, anthropologists' reports, satellite data, historical patterns of the Southern Oscillation Index (SOI), and rainfall records.
The earliest evidence found for pre-European megafires came from Aboriginal mythology. Among other fire myths, one in particular preserves an oral history of a fire in west-central Australia that would have conservatively covered 12.6 million ha.
Other evidence came from the records of explorers like Ernest Giles and Colonel Egerton-Warburton, who traversed the Australian inland in the early 1870s. Although the country the explorers travelled through was visibly under Aboriginal management, they reported fires that burnt for "scores of miles", implying that sometimes hundreds of thousands of hectares had been burnt in a single blaze.
More recent evidence for the link between climate and megafire came from remote imagery of west-central Australia in the early 1980s.
After a burst of vegetation growth in 1982 following a big rainfall event, the satellite data showed that fires burned across 1.4 million hectares of desert. Despite this natural fuel-reduction event, huge fires swept the region again in 1985, burning 472,000 ha that had been burned in the 1982-83 fires and just over a million hectares in total.
Given there are parallels between this research and the climate–fire linkage in the Eucalypt-dominated forests of temperate Australia, Dr Wright and his colleagues hope their work will lead to more fire research Australia wide.
“The current demand by governments to burn a proscribed area of the natural estate each year makes unreasonable demands on land managers and has uncertain effects on plants and animals”, Dr Wright observes.
"Another big concern is that under climate change, megafires are likely to be more frequent and more intense. We need to prepare for that reality, and not imagine that patch burning will solve our problems. Immediate action to mitigate greenhouse gas emissions is essential as megafires under climate change are likely to be even more catastrophic…"
Rainfall-Linked Megafires as Innate Fire Regime Elements in Arid Australian Spinifex (Triodia spp.) Grasslands. doi: 10.3389/fevo.2021.666241
